#include<iostream>
#include<vector>
using namespace std;

int longestPalindromeSubseq(string s) {
    int n = s.size();
    vector<vector<int>> dp(n, vector<int>(n));
    int len = 1;

    for (int i = n - 1; i >= 0; i--) {
        dp[i][i] = 1;
        for (int j = i + 1; j < n; j++) {
            if (s[i] == s[j])
                dp[i][j] = dp[i + 1][j - 1] + 2;
            else
                dp[i][j] = max(dp[i + 1][j], dp[i][j - 1]);
        }
    }

    return dp[0][n - 1];
}

int main()
{
    string s = "bbbab";
    cout << longestPalindromeSubseq(s) << endl;
    return 0;
}